Not applicable.
(1) Field of the Invention
The present invention relates generally to systems and methods for closed cycle thermal propulsion systems and, more particularly, to methodology for estimating performance, including off-design performance, for closed cycle thermal propulsion system.
(2) Description of the Prior Art
Closed cycle thermal propulsion systems are well known and may often be utilized to propel torpedoes through the water. Generally, design parameters for the propulsion systems of torpedoes are based on assumptions such as, for instance, anticipated torpedo speed and range as well as the anticipated torpedo length and diameter. Prior to the present invention, there was no available means to determine how the torpedo would perform based on off-design criteria, e.g., if various kinematic maneuvers were made, different speeds utilized, different torpedo lengths and diameters were used, and so forth. Such capability may be of particular use for special mission requirements that may utilize existing equipment.
Various inventors have attempted to solve related problems as evidenced by the following patents, without providing the solutions taught hereinafter.
U.S. Pat. No. 5,291,390, issued Mar. 1, 1994, to Nobuyasu Satou, discloses a control apparatus for a mechanical device including a control element for receiving a reference input signal and supplying an operating signal to the mechanical device, a main feedback element for detecting the control signal and supplying the detected control signal to the control element, and an auxiliary feedback element for detecting the operating signal to be supplied to the mechanical element and supplying the detected operating signal to the control element. The control element produces the operating signal based on the reference input signal, the control signal supplied from the main feedback element, and the operating signal supplied from the auxiliary feedback element to regulate the control speed such that hunting in the control apparatus does not occur.
U.S. Pat. No. 5,117,635, issued Jun. 2, 1992, to Alfred Blau, discloses a unique arrangement of components comprising an open Rankine cycle power system for underwater application. The arrangement features a high energy density steam generator, a turbine, pumps and other apparatus to provide and control the flow of a seawater working fluid and the use of a mixing condenser the spent steam. The mixing condenser uses droplets of seawater to condense the steam exhausted from the turbine. Alternatively, the steam may be introduced into a pool of water in the mixing condenser by means of a bubble device. The mixing condenser also provides a preheated feedwater supply for the boiler. This system facilities the packaging of power sources an order of magnitude more powerful than current sources. Moreover, this system can be installed in current vehicles.
U.S. Pat. No. 4,991,530, issued Feb. 12, 1991, to Alan D. Rathsam, discloses a fin apparatus for controlling heat flux distributions in a heated body, such as a torpedo. The torpedo may have inner and outer spaced apart shells with a predetermined ratio of conducting and nonconducting fins affixed to the shells in the space there between. In a torpedo it is desirable to establish the ratio so that heat will be distributed form the outer skin of the torpedo shell to improve laminar stability in the boundary layer as the torpedo travels through the water.
U.S. Pat. No. 4,846,112, issued Jul. 11, 1989, to Buford et al., discloses an ullage compensator for a stored chemical energy power propulsion system. With the invention, at least one moveable wall is provided within a reactor having a chamber which is moveable between a first position at which the chamber has a maximum reaction volume to a second position at which the reaction chamber has a minimum volume. A force is applied to the moveable wall by a bellows to cause the wall to project into the chamber in response to the force when a reaction is occurring within the chamber. The invention eliminates damage to the interior surface of the chamber and the inlet port(s) for introducing an oxidant into the chamber with sustains the reaction caused by direct contact with a gaseous oxidant which causes the reaction.
U.S. Pat. No. 4,680,934, issued Jul. 21, 1987, to Keith E. Short, discloses a construction including a housing having an interior wall, defining a chamber with at least one oxidant inlet, in which weight, noise and response difficulties in boilers utilized in torpedoes are eliminated. A pluarality of working fluid conduits each have an inlet and an outlet exterior of the housing and heat exchange section within the chamber. Each heat exchange section is a plural convolution coil and the individual convolutions of each conduit are interleaved with the individual convolutions of the other conduits. Valves control the flow of working fluid through at least some of the conduits independently of the others.
U.S. Pat. No. 4,658,589, issued Apr. 21, 1987, to Thomas A. Sutrina, discloses an ejection system including a steam ejector having a steam nozzle aligned with a diffuser which defines an outlet from the ejection system. The ejector has an inlet to the interface of the nozzle and the diffuser. A normally closed, non-condensable flow control valve has an outlet connected to the ejector inlet and an inlet adapted to be connected to a working fluid flow path of a Rankine cycle apparatus. A motor is provided for selectively operating the flow control valve. A steam generating reaction chamber is in fluid communication with the steam nozzle and first and second pressure vessels are provided and adapted to contain a different reaction. A valve controls fluid communication between the pressure vessels and the reaction chamber.
U.S. Pat. No. 4,637,213, issued Jan. 20, 1987, to Lobell et al., discloses an arrangement for a thermal, steam-powered engine in a submarine vehicle, for example a torpedo. A condenser is so arranged as to separate the exhaust from the engine into a condensable exhaust fraction and into a non-condensable exhaust fraction. A compressor, which is connected to the engine for the purpose of silencing, is so arranged as to compress only the non-condensable exhaust fraction which, after compression is discharged through an exhaust outlet into the surrounding sea water. The condenser is in the form of a sleeve which for silencing purpose encloses both the engine and the compressor. A sound-deadening gap is arranged between the condenser and the hull of the vehicle.
U.S. Pat. No. 4,598,552, issued Jul. 8, 1986, to Kent Weber, discloses an energy source for a closed cycle engine including a boiler having a working fluid chamber in heat exchange relation with a reaction chamber. A closed flow path loop including a turbine receives working fluid from the fluid chamber, provides a power output and returns the fluid to the chamber. Lithium is reacted with water in the reaction chamber to generate heat for heating the working fluid and hydrogen. Oxygen, obtained by decomposition of sodium superoxide elsewhere in the system, is fed to the reaction chamber and combined with the hydrogen to provide water and additional heat for the working fluid.
U.S. Pat. No. 4,597,345, issued Jul. 1, 1986, to Resser et al., discloses a communications link between a submarine and a torpedo secured within launch tube flooded with seawater. A transmit/receive light beam pair propagating through the water provides the high bandwidth data channels between the tube wall and the adjacent torpedo hull for two-way communication.
The above patents do not disclose a method for estimating off-design operating parameters including steady state operating characteristics for closed cycle thermal propulsion systems. For instance, the above patents do not teach determining propellant consumption for a torpedo as a result of various kinematic maneuvers. As another example, the above patents do not teach how to estimate total torpedo run time if the torpedo speeds, lengths, diameter, and so forth are altered from the original design. Consequently, there remains a long felt but unsolved need for improved determination of torpedo characteristics that may be utilized to define weapon design options in fulfill future mission effectiveness requirements. Those skilled in the art will appreciate the present invention that addresses the above and other problems.
Accordingly, it is an objective of the present invention to provide an improved system and method for determining performance characteristics of propulsion systems.
Another objective is to provide a system and method as aforesaid which may be utilized to determine off-design characteristics of a closed cycle thermal propulsion system.
A further objective is to provide a system and method as aforesaid whereby propellant consumption for a torpedo may be determined as a result of various kinematic maneuvers.
These and other objectives, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims. However, it will be understood that the above listed objectives and advantages of the invention are intended only as an aid in understanding aspects of the invention, and are not intended to limit the invention in any way, and do not form a comprehensive list of objectives, features, and advantages.
In accordance with the present invention, a system is provided for a method for determining one or more off-design performance characteristics for a closed cycle thermal propulsion system which may comprise one or more steps such as, for instance, providing design characteristics of the closed cycle thermal propulsion system, inputting off-design requirements for the closed cycle thermal propulsion system, and determining the one or more off-design performance characteristics of the closed cycle thermal propulsion system in response to the off-design requirements.
The off-design requirements may comprise one or more legs, or segments of differing speed/time duration profiles, of a route, or run of, a vehicle powered by the closed cycle thermal propulsion system, and providing a speed and time duration for each of the one or more legs wherein the method may comprise determining propellant consumption for the one or more legs. The method may be utilized in the case wherein a different speed is utilized for each of at least two legs. The method may further comprise determining total run time in response to the off-design requirements.
The off-design requirements may also comprise vehicle configurations of different lengths and diameters powered by the closed cycle thermal propulsion system.
In one preferred embodiment, the may further comprise iteratively determining off-design turbine parameters such as parameters related to off-design turbine efficiency. The method may further comprise determining propellant consumption rate at an off-design speed. Moreover, the method may further comprise determining parameters related to steam flow rate at an off-design speed and/or determining the propellant consumption rate for the off-design speed by utilizing the steam flow rate at the off-design speed.
In other words, a method is provided that may comprise one or more steps such as, for instance, providing design characteristics of the closed cycle thermal propulsion system comprising a design for a vehicle powered by the closed cycle thermal propulsion system and/or determining the one or more performance characteristics of the closed cycle thermal propulsion system in response to one or more off-design speeds for the vehicle.
Other steps may comprise determining a turbine working fluid flow rate at the one or more off-design speeds and/or utilizing the turbine working fluid flow rate to determine propellant consumption at the one or more off-design speeds.
Thus, the method may also comprise providing design characteristics of the closed cycle thermal propulsion system, inputting off-design requirements that may comprise one or more legs of a route for a vehicle powered by the closed cycle thermal propulsion system, and providing an off-design speed and a time duration for each of the one or more legs, then determining the one or more off-design performance characteristics of the closed cycle thermal propulsion system in response to the off-design requirements.